WAD300BPP - extraordinary amplifier

[andrew ivimey]

It occurs to me that the 300mv input is a little tricky.

Why not rewire for 5687 as input valve instead of the otherwise totally superb6072; gain goes down nicely and welly goes up - much better Ra or I'm a monkey's uncle!

Superb amplifier, though!

yours, Johnnie come lately

Oh you actually have the nerve to enjoy the amplifier, how very dare you :p

[Andrew]

Did you buy one, Andrew?

[Richard]

You could try ECC82(17) 6072(44) ECC81(60) 5751(70) and ECC83(100) in there first Jonnie without rewiring. I didn't find drive an issue and prefer it without a bypass cap which raises Ra in fact, but lowers distortion and sensitivity, and the whole amp then measures superbly to boot, have fun

Rich

[Greg.]

Hi Andrew,

OK, you've discovered something. Excellent but please stop talking in riddles. If you have something to offer on development of the WAD 300B PP, I'm seriously interested (as several others are) but without doubt we want it in plain simplistic directional English. Some of us (certainly I am) are thick. A clear directional explaination would be very good for all of us. As much as I try to reach up to understand the interlect of your postings, with no offence intended, generally I struggle to make sense of what you post albeit I know it is all in there one way or another. On this occasion I simply ask you to explain simply what you have done that in your view makes the amp perform better.
Otherwise, I'll need to tie you down at Owston and not release you until I understand what you are going on about..........that might mean you miss out on your supper. Shame

Best wishes,

Greg

[richardcooper2k]

do you think he likes cryptic crosswords ?

[Ianm2]

I can't see what's cryptic, he's simply saying lower gain and ra by using 5687 as the input.

I liked ecc81 and 5751 best as input and e182cc as driver, but may need a little attention measurement wise, its very full on.

[andrew ivimey]

I'm not coming to Owston! I didn't realise the awesome responsibility I was taking on when I snapped up this gorgeous amplifier.

All I thought I was getting was a chance, a glimpse of Heaven.

I've put in quite a lot of soldering iron time and more than a week of sleepless nights, tossing and er .... well anyway.

I have been mightily surprised at how good this amp sounds. Perhaps I shouldn't have been so surprised. I really was buying it only on the off chance that it (c)would work well and that chassis is 'to die for' looks wise. An Amity Mk4 was to come out of it! But No, this one gets a total full chance to prove itself.

So, to valves. Why I didn't just pop in an ecc82 for example is that they are the devil's drab greyness but otherwise(!) it might help. 6072s and 5687s are relationships made in Nirvana as Audionote testify but with this combo. isn't quite right, imho, so then Richard's suggestions could be worked through - give me a year to try them all!

But a 5687's qualities could shine through here, just maybe. And, a faint echo in my mind suggests that didn't Max's 300BPP monster (also designed my young Mr Grove) begin with a 5687?

food for thought!

Oh yes, and I am very impressed with the transformers in this amp. If SPWound provided all the trafos for WAD, they pulled out all the stops on this set. Thunderous praise! I was ready to replace them with Lundahls and O-Netics. I am not now.

And, am I right in thinking that SPWound is based in Poole. I have, when I could afford it, used Majestic Transformers and I think they too are based in Poole. I have no reservatios about Majestic's marvellous iron, their quick turnaround and personal service whatsoever. Are they related in any way, I wonder?

[steve s]

Greg i hope you dont mind me explaining...

most cd players put out a couple of volts into the amp

the sensitivity of an amplifier is how much voltage it needs on the input to give the rated output

this amp is designed to take up to 300mv, less than a 1/3rd of a volt.. so putting putting a cd player on it will/ may overdrive the amp if you turn it up very loud ... so there is gain being wasted... unless your using a low voltage source.. but as most use a cd player...

andrew is looking at puting a valve with less gain to change the sensitiveity of the amp, also by using a valve with less gain.. they usually draw more current which 'can' improve thing slightly,

there is a whole balancing act when building amps with the gain of the stage(s) vs number of stages.. many like lots of low gain stages and some don't.. which is best ?? i think it depends more on the valves used..

to explain that in a little more detail, there is a thought that more current on the grid of a valve, gives more control to the output of that valve..
this may or may not be the case, in my view, this seems more critical further up the amp.. ie feeding the grid of output valves.. where larger voltages and physically larger control grids are the norm.. but many may not agree...

hope thats some use


cheers steve

[Ianm2]

300 mVolts, steve.

yes sensitivity means 300mv in will drive it to 28 watts out or whatever it will give.

so you have a cd which gives 2 volts, you need to cut it with a volume control, and low down, there obviously isn't many watts at all coming out, so you have very little millivolts going in.

if you put in a valve with a lower mu (gain) than the 6072, I think its 44? or 60 ish, it will mean you need to put in more volts to get full output power, which is measured in watts of course, you can translate that to volts out with the power equation.

I played with this amp a lot, I think it has a certain magic, I am not a fan of 6072 nor 5687 massively, I found they were slightly bland myself.

I found the amp a little thick sounding at times, but very very good.

I had one with a blown tx, I dismantled it.

it has 5 layers, 3 primaries interleaved with 2 secondaries, probably the minimum to get a reasonable leakage inductance, ie coupling between primary and secondary so the treble doesn't roll off.

the insulation was 3 layers of masking tape and yellow polyester tape I think

very standard really

I dunno if grove or geoff designed the tx's, geoff claimed to

If you want to max it out, I would use 2 mains tx's, mono it, and replace the outputs with the monster sowter 7kohms, very expensive, may not sound better, but if you have cash to spare its gotta be tried.